fuelsforum.rasoenterprises.com
Franz and Frank as well as many other on there are very knowledgeable. IIRC Frank is a member here.
FWIW, I had a 1989 F350 Crewcab 4x4 with a 460/5speed, had 4.10 gearing and 235/85 r16 tires. So you can imagine it revved pretty high (no tach for exact rpm) somewhere around 3000rpm at 110 km/h or about 70mph. The truck had 380,000km on it (238,000 miles) and the oil in the pan was still as clean as the day the truck would have rolled off the line. Im guessing it had been on
propane its whole life. The truck ran extremely nice, very very well. Those are the upsides.
The downside, it cost me about $30 when
propane was around $0.80/liter ($3.20 gallon) to go 110km (70miles) about 80% of that was highway.
Just throwing that out there for some info for you.